1. Field of the Invention
This invention relates to the preparation of amide derivatives of acids by a novel reaction which combines the amino group of a haloaminotriazine with the non-halide portion of an acid halide. The reaction also combines the halogen atom of said haloaminotriazine with the halogen atom of the acid halide producing a halogen molecule as a by-product. This invention is also directed to a novel process of preparing isocyanates and isocyanate adducts from haloaminotriazines and selected acid halides.
2. Related Background Art
Amides can be prepared by the reaction of amines with acid halides. Although the reaction of amines with acid chlorides is quite general, it is sluggish and often fails to take place if the amine is deactivated by the presence of at least one electron withdrawing substituent. In some cases, preparation of an amide may be possible by first deprotonating the amine with a strong base to generate an anion and then allowing the amine to react with the acid halide. This approach, however, is often impractical, costly, and very limited in scope, and is inoperative if the amine has low solubility, high molecular weight, or both.
Tris-carbamates have been prepared by converting an aminotriazine to an isocyanate group, by reacting the aminotriazine with oxaylyl chloride, followed by reaction with an alcohol. This two step approach described in U.S. Pat. Nos. 4,939,213 and 5,084,5. The patents also describe curable compositions using triazine tris-carbamates. The preparation of other carbamates by the above mentioned approach is described in an article by U. Von Gizycki in Angewandte Chemie, International edition, Volume 10, page 403, (1971), entitled "Isocyanato-s-Triazines." The author states therein that until that time, only one isocyanato-s-triazine, namely the 2,4-dichloro-6-isocyanate, derivative had previously been isolated, and that from tetrameric cyanogen chloride by a route that cannot be generalized.
Partially successful attempts to prepare mono- and bis-carbamates from aminotriazines and haloformates are described in an article entitled "Melamine Derivatives 18: Reactions of Melamine and Benzoguanamine with Ethyl Chlorocarbonate" by H. Kitajima, T. Imanaka, and T. Yamomoto in Yuki Gosei Kagaku Kyokai Shi, Volume 32, Number 9, pages 723 to 726 (1974); Chemical Abstracts Volume 82, Number 11: 72946d. The article, however, does not mention the preparation of tris-carbamates.
Preparation of halomelamines are disclosed in U.S. Pat. Nos. 2,184,888; 2,184,886; 2,184,883; 3,743,642; and 2,472,361; in South African Patent No. 66-03546; and in European Patent No. 239,121. The reaction of oxalyl chloride with N,N-dichloroalkylamines or N,N-dichloroamides, to form N-chloro-N-alkyloxamyl chlorides or isocyanates, is disclosed in Chemical Abstracts, Vol. 75 (21), item 129306g, condensed from a Russian Language article in Zh. Org. Khim., Vol. 7, No. 7, p. 1541 (1971). The reaction of N-chlorocarboximidic esters with oxalyl chloride is disclosed in Chemical Abstracts, Vol. 72 (17), item 90006v, condensed from a Russian Language article in Zh. Org. Khim., Vol. 6, No. 1, p. 85-88 (1970).
It is well known that the chemistry of amines and triazines is quite different. In a publication by E. M. Smolin and L. Rapaport entitled "S-Triazines and Derivatives" Interscience Publishers Inc., New York, page 333 (1959), it is reported that attempts to react an acid halide with the amino group on a triazine such as melamine have not been successful. Likewise, the reaction of melamine with alkyl halides, such as allyl chloride, is known to result in alkyl substitution at the nitrogen on the triazine ring resulting in isomelamine derivatives.
Melamine chemistry, particularly halomelamine chemistry including preparation and applications, is discussed in an article by B. Bann and S. A. Miller entitled "Melamine and Derivatives of Melamine", Chemical Reviews, Volume 58, pages 131 to 172, (1958). It is stated therein on page 148 that acyl halides such as benzoyl chloride in the Schotten-Baumann reaction have no effect on melamine. The inertness of melamine towards acid halides is further described in Chemical Abstracts Vol. 30, p. 465 (1936) and in U.S. Pat. No. 2,557,418.
In view of the reported difficulties encountered by practitioners in the fields of melamine and triazine chemistry, a novel chemical reaction which overcomes the aforementioned difficulties and provides a general method for preparing acylated aminotriazines from widely available haloaminotriazine precursors would be a valuable addition to the very limited methods available to date. When not commercially available, the haloaminotriazines are easily prepared by well known methods.
It is the object of this invention to provide a simple process for preparing amides from haloaminotriazines and acid halides.
It is also an object of this invention to provide a process for preparing isocyanates starting from haloaminotriazines and acid halides.
Another object of this invention is to provide a process for preparing isocyanate adducts starting from haloaminotriazines and acid halides.
This invention involves a novel chemical reaction which combines the amine group of a haloaminotriazine with the non-halide portion of an acid halide to produce an acid amide and recyclable halogen. The preparation of isocyanates is accomplished by decomposing specific acid amides to the isocyanates and the isocyanate adducts are then prepared by reacting the isocyanates with active hydrogen-containing compounds.